"Bailout Bevin: Not a Kentucky conservative," the ad closes.
It's backed by a six-figure buy and was launched alongside BailoutBevin.com, a website detailing the financial history of Bevin's family's business on which the McConnell campaign will release more information in the future.
McConnell has previously run positive spots characterizing himself as a "Kentucky conservative," in an attempt to protect himself against a long-expected challenge from the right.
That challenge comes in Bevin, who is kicking off his run on Wednesday.
The McConnell campaign insisted it wasn't worried about what campaign manager Jesse Benton called a "nuisance" candidate, but warned that they'd have a "welcome wagon" of attacks, and planned to inform voters Bevin is “a chronic tax delinquent who fails to pay taxes and yet goes to government for handouts and bailouts.”
The new ad refers to the $200,000 in state grants Bevin obtained to help his family's bell-making company rebuild after a 2012 fire, as well as a number of tax liens the company was assessed with for failing to pay $116,000 in taxes.
The company was characterized in 2011 in a local newspaper as the number one tax delinquent firm in East Hampton, Conn.
A spokesperson for Bevin said that he hadn't taken over complete control of the company until August 2011, after which he paid off the back taxes, and personally loaned the company $1 million to help do so. The spokesperson also said that Bevin had paid back most of the state grants.
Though his campaign says otherwise, the early attack is an indication McConnell is taking the challenge seriously. He's long been considered vulnerable to a Tea Party challenge, as conservatives are frustrated with his votes for the financial bailout and to raise the debt ceiling, as well as his support for the previous immigration overhaul.
Those votes are the focus of Bevin's first ad in the race.
"McConnell has voted for higher taxes, bailouts, debt ceiling increases, congressional pay raises, and liberal judges," a narrator says in the ad.
The ad goes on to introduce Bevin as having "small town roots; successful businessman; father of nine; military veteran; conservative, Republican, for U.S. Senate."
McConnell has worked to shore up support on his right flank, gaining the endorsement of Tea Party favorite Sen. Rand Paul (R-Ky.) and hiring Benton, who managed Paul's campaign.
His efforts have thus far proved to be unsuccessful, however, as Bevin is entering the race Wednesday. McConnell is also facing Democrat Alison Lundergan Grimes on the right.